The invention relates generally to optical networks and, more particularly, to testing components in an optical network.
In an optical network, a signal may go through many optical components while traveling along a network path between a source node and a destination node. The form of the path may be selected through mechanical optical switches distributed through the network. Some conventional switches employ movable refractive plates to select the switch connectivities defining the path.
If any component along the path of a signal functions poorly, the signal received at a destination node may be of poor quality. To determine why a received signal is of poor quality, a system manager must generally test each optical component along the network path taken by the signal.
Testing each component along an optical path may be difficult, because the paths are large or inaccessible. The paths may be long, because the optical network may span more than a hundred miles. The network components, e.g., optical fibers, can also have dimensions of tens or hundreds of miles. In smaller optical networks found in optical devices, the optical paths may be inaccessible. For example, some optical devices enclose the optical network in a sealed box, which is difficult to look inside or open.
A network can be tested by transmitting a signal into the network and detecting the signal at remote monitoring points. The detector may use active monitoring devices located at the remote points, e.g., photo-detectors. The active devices may be either permanently or temporarily inserted into the signal path. Permanently inserted devices can reduce optical signal intensities. Temporarily inserted devices may be difficult to use due to the size of network components and may be expensive due to the number of devices needed to monitor the whole network.
Other prior art techniques for testing an optical network are manual and involve inserting a patch cord at a remote location to monitor signals. Manual testing of signal networks having many optical components can be slow. Such manual testing methods can produce unacceptably long down times.
The present invention is directed to overcoming, or at least reducing, one or more of the problems set forth above.
In a first aspect, the invention provides an optical network for transmitting optical signals between a plurality of nodes. The optical network includes a plurality of optical conduits and a plurality of optical switches. Each node couples to one of the optical conduits. The optical switches have ports coupling to the optical conduits to form connected paths between associated pairs of the nodes. The paths have first and second modes of operation. In the first mode, one of the paths transmits an optical signal between the associated pair of nodes. In the second mode, the one of the paths transmits an optical signal from a node through a partial portion of the path and reroutes the same optical signal back to the same node.
In a second aspect, the invention provides a method of testing a component of an optical network. The method includes transmitting an optical signal from a node of the optical network through a path that the component is on and passively looping the same optical signal back to the node. The method also includes analyzing the passively looped back optical signal.
In a third aspect, the invention provides an optical switch for routing optical signals between ports of the switch. The switch includes a refractive plate that may be oriented to passively loop back an optical signal from one of the ports to the same one of the ports.
In a fourth embodiment, the invention provides an optical switch to reroute incoming optical signals. The optical switch includes a plurality of ports to hold optical fiber ends, a focusing reflector to reflect light incoming from the ports, and a plurality of refractive plates. The refractive plates are located along paths of light rays going from the ports to the focusing reflector. Each refractive plate has two working orientations. A loop back arrangement of the working orientations reroutes light incoming from one of the ports to the focusing reflector and back to the same one of the ports.